1. Field of the Invention
The invention relates to a printing apparatus using an ink-jet head and a method of filling an ink-jet head with a liquid. More particularly, it relates to an apparatus for manufacturing a micro-array, which prints liquid spots of many kinds in very small volumes, like an apparatus for manufacturing a micro-array of DNA, proteins, etc. and a method of filling an ejection head thereof with a liquid.
2. Related Art
Ink-jet type printing apparatuses are in wide and general use as ink-jet printing apparatuses. Some of the advantages of ink-jet printing apparatuses are that ink-jet heads can be made small and with high density, that they can place small volumes of liquid drops at desired locations with high precision, that they are unaffected by the type or properties of the ejected liquid, that they can be used for printing on arbitrary media besides paper, including film, fabric, glass plate, synthetic resin substrate, and metal plate, that they make little noise while printing, and that they are inexpensive.
For these reasons, ink-jet technologies have received much attention in recent years for applications in many sectors besides the main sector of printing, for example, manufacturing DNA chips (also called DNA micro-arrays). Here, ‘DNA chips’ means, for example, chips on which solutions containing several thousand or several tens of thousands of DNA fragments have been attached in a matrix pattern to a substrate, for example, slide glass, for genetic classification or analysis.
Ink-jet printing apparatuses and other apparatuses require filling (priming) the all nozzles of ink-jet heads or ejection heads with a liquid to be ejected (ink, etc.).
Conventionally, such priming is carried out in ink-jet printing apparatuses by the method of evacuating the ink chamber via nozzle opening faces, a suction cap brought into close contact with the nozzle opening faces on the ink-jet head, and pumping the air out.
However, since it is difficult to detect when each nozzle has been completely filled with ink, suction time of the pump is extended somewhat. As a result, some ink is wasted because it is released from the nozzle tip.
A method of manufacturing a DNA chip by the ink-jet method is also disclosed in, for example, Japanese Laid-Open under the Public No. 2001-186880, but that patent has two problems: first, that it applies to filling nozzles all the way up to the tip with very small volumes of biopolymer solutions; and second, that a small volume of the expensive biopolymer solution is wastefully discarded when used in the same method for priming as in conventional ink-jets.